I recently realized that our 3-tier descriptive URL system (as /tab/category/item) is hurting us in google because each product has multiple pages if it's included in multiple categories. This means that are competing for rankings AND I'm being penalized for duplicate content.

I decided that changing to the single descriptive URLs (as /category or /item) would solve this problems... each item will only have one URL (/item_name) so there will be no duplicate content and all the traffic will be going to one page, so there won't be duplicate content duking it out for rankings, right?

Wrong... I've realized that when I switch to the short URLs, Netsuite is going to put query strings on the end of them in order to show which of the multiple categories the user clicked through.